The quantitative determination of analytes in body fluids is of great importance in the diagnoses and maintenance of certain physiological abnormalities. For example, lactate, cholesterol and bilirubin should be monitored in certain individuals. Additionally, determining glucose in body fluids is important to diabetic individuals who must frequently check the glucose level in their body fluids to regulate the glucose intake in their diets. While the remainder of the disclosure herein will be directed towards glucose determination, it is to be understood that the methods of this invention may be used for determining other analytes on selection of an appropriate enzyme.
The results of such tests can be used to determine how much, if any, insulin or other medication needs to be administered. In one type of blood glucose testing system, test sensors are used to test a sample of blood.
A test sensor typically contains biosensing or reagent material that will react with blood glucose. A testing end of the sensor is adapted to be placed into the fluid being tested, for example, blood that has accumulated on a person's finger after the finger has been pricked. The fluid is drawn into a capillary channel that extends in the sensor from the testing end to the reagent material by capillary action so that a sufficient amount of fluid to be tested is drawn into the sensor. The fluid then chemically reacts with the reagent material in the test sensor. The current generated by the electrochemical reaction is converted into a measurement that is indicative of the analyte level in the fluid being tested.
To couple the electrical signals produced at the test sensor contacts to monitoring equipment, the sensors need to be inserted into sensor holders prior to the sensor end being placed into the fluid being tested. The holders have corresponding mating contacts that become coupled to the contacts on the test sensor when the sensor is properly inserted into the holder. Consequently, the holders act as an interface between the test sensor and monitoring equipment that accumulates and/or analyzes the test results.
Most test sensors need to be maintained at an appropriate humidity level prior to being used so as to insure the integrity of the reagent materials in the sensor. Test sensors can be packaged individually in tearaway packages so that they can be maintained at the proper humidity level. For instance, blister-type packaging methods may be used. In this connection, the packages can include desiccant material to maintain the proper humidity in the package. For a person to use an individual test sensor for testing an analyte, the package may be opened by tearing the seal. Alternatively, some packages require the user to exert force against one side of the package resulting in the test sensor bursting or rupturing the foil on the other side. As can be appreciated, the opening of these packages can be difficult. Moreover, once the package is opened, the user needs to be sure that the test sensor is not damaged or contaminated as it is being placed into the sensor holder and used to test the fluid sample.
In certain sensor-dispensing devices, a stack of disposable test sensors is provided within a cartridge and the stack is pushed or urged towards a test station where testing occurs. A pushing mechanism is inserted into a first opening on one end of the cartridge, through which the mechanism contacts the stack of sensors. Typically, the pushing mechanism moves the top most sensor in the stack through a second opening that is usually located on the opposite end of the cartridge from the first opening toward a testing station. Therefore, the use of a pushing mechanism requires the presence of two openings in the cartridge. Cartridges having two openings may present problems with sealing the cartridge in order to preserve the shelf-life of the remaining sensors within the cartridge.
In some sensor-dispensing devices, the mechanism for moving a sensor from a stack of test sensors is located in the disposable cartridge that houses the stack of sensors. In other words, every time the empty cartridge is discarded, the mechanism for moving the sensor is also discarded, thereby raising the cost of replacing the cartridge.
In some sensor dispensing devices that use disposable cartridges, the mechanisms that seal the sensor within the cartridge and permit the sensor to be removed from the cartridge are designed to be physically attached to the cartridge. Therefore, every time the cartridge is depleted of sensors and must be replaced, the sealing mechanisms must also be replaced, thereby adding to the cost of replacing the cartridge.
Accordingly, it would be desirable to have a sensor-dispensing device and a mechanism for extracting a sensor that overcomes the problems discussed above.